FIG. 12 shows a conventional information recording medium 1201 and an example of a data structure of a channel signal 1203 to be recorded in the information recording medium 1201.
The channel signal 1203 is recorded on the information recording medium 1201 by a pickup 1202. The channel signal 1203 recorded on the information recording medium 1201 is reproduced by the pickup 1202.
The channel signal 1203 includes a plurality of SYNC codes and a plurality of modulated codes. Data is obtained by decoding the plurality of modulated codes included in the channel signal 1203.
FIGS. 13 and 14 each shows an example of sector data structure recorded on the information recording medium 1201.
Usually on the information recording medium 1201, coded data is recorded. A typical coding method is a digital modulation such as, for example, an 8-16 modulation method. Such a digital modulation restricts a frequency component of a signal to a certain level or less.
A SYNC code is inserted into the modulated data at a prescribed interval. The SYNC code has a special pattern which never appears in the modulated data. Insertion of such a SYNC code has the following advantage. When a bit shift is generated while data is being read, a SYNC code is reset at a correct bit position when the SYNC code is detected. Thus, data can be correctly read thereafter. A unit of data for which a SYNC code is provided is referred to as a “SYNC frame”.
A sector includes at least one SYNC frame. A sector is provided with a sector address (i.e., a serial number for the sector). A sector address is recorded at a specific position of the sector (for example, at the head of a first SYNC frame).
The modulated SYNC frame data (modulated code) is demodulated, which is opposite to a modulation, so as to collect one sector of SYNC frame data. In this way, post-demodulation (post-decoding) sector data is obtained. At least one piece of such sector data is collected and rearranged so as to obtain a data structure. For this data structure, an error correction code (ECC; for example, a Reed-Solomon code) is formed.
At least one sector, which is a unit for which error correction is performed, is referred to as an “error correction block (or ECC block)”. An ECC can correct a data error in a certain range. As a result, even when a bit shift is generated while the data is being read, correct data can be obtained at the end, as described above.
FIG. 13 shows an example of a sector data structure. In the example shown in FIG. 13, a SYNC code is either SY0 or SY1. The SYNC code SY0 is located at the head of a first SYNC frame, and the SYNC code SY1 is located at the head of each of second through 26th SYNC frames. Such location of the SYNC codes is advantageous for distinguishing the first SYNC frame of one sector from the other SYNC frames.
Assignment of two different types of SYNC codes to the SYNC frames as described above has an advantage that the head of the sector can be recognized without demodulating the modulated data (modulated code).
FIG. 14 shows another example of a sector data structure. The sector data structure is of a DVD (Digital Versatile Disk). In the example shown in FIG. 14, the SYNC code is either one of SY0 through SY7. The SYNC code SY0 is located at the head of a first SYNC frame. The SYNC code SY1 is located at the head of each of third, 11th and 19th SYNC frames. The SYNC code SY2 is located at the head of each of fifth, 13th and 21st SYNC frames. The SYNC code SY3 is located at the head of each of seventh, 15th and 23rd SYNC frames. The SYNC code SY4 is located at the head of each of ninth, 17th and 25th SYNC frames. The SYNC code SY5 is located at the head of each of second, fourth, sixth, eighth and tenth SYNC frames. The SYNC code SY6 is located at the head of each of 12th, 14th, 16th and 18th SYNC frames. The SYNC code SY7 is located at the head of each of 20th , 22nd, 24th and 26th SYNC frames. Such location of the SYNC codes are advantageous for specifying the position of the SYNC frame in one sector.
Assignment of eight different types of SYNC codes to the SYNC frames as described above has an advantage that the position of the SYNC frame in one sector can be recognized without demodulating the modulated data (modulated code).
The position of the SYNC frame in one sector are specified as follows in accordance with the sequence (recording order) of two SYNC codes included in two successive SYNC frames.
(SY7, SY0): first SYNC frame,
(SY0, SY5): second SYNC frame,
(SY5, SY1): third SYNC frame ((SY0, SY5, SY1)),
(SY1, SY5): fourth SYNC frame,
(SY5, SY2): fifth SYNC frame,
(SY2, SY5): sixth SYNC frame,
(SY5, SY3): seventh SYNC frame,
(SY3, SY5): eighth SYNC frame,
(SY5, SY4): ninth SYNC frame,
(SY4, SY5): tenth SYNC frame,
(SY5, SY1): 11th SYNC frame ((SY4, SY5, SY1)),
(SY1, SY6): 12th SYNC frame,
(SY6, SY2): 13th SYNC frame,
(SY2, SY6): 14th SYNC frame,
(SY6, SY3): 15th SYNC frame,
(SY3, SY6): 16th SYNC frame,
(SY6, SY4): 17th SYNC frame,
(SY4, SY6): 18th SYNC frame,
(SY6, SY1): 19th SYNC frame,
(SY1, SY7): 20th SYNC frame,
(SY7, SY2): 21st SYNC frame,
(SY2, SY7): 22nd SYNC frame,
(SY7, SY3): 23rd SYNC frame,
(SY3, SY7): 24th SYNC frame,
(SY7, SY4): 25th SYNC frame, and
(SY4, SY7): 26th SYNC frame.
By distinguishing the sequence of two SYNC codes included in two successive SYNC frames, the first and 2nd SYNC frames can be distinguished from each other, the fourth through tenth SYNC frames can be distinguished from each other, and the 12th through 26th SYNC frames can be distinguished from each other.
Depending on the sequence of two SYNC codes included in two successive SYNC frames, the third SYNC frame and the 11th SYNC frame cannot be distinguished from each other. In both of the third SYNC frame and the 11th SYNC frame, the SYNC codes are arranged as (SY5, SY1). In this case, a SYNC code immediately before SY5 can be added to distinguish the SYNC frames. When the SYNC code immediately before SY5 is “SY0”, the SYNC frame is determined to be the third SYNC frame. When the SYNC code immediately before SY5 is “SY4”, the SYNC frame is determined to be the 11th SYNC frame.
FIG. 15 shows an NRZ (Not Return Zero) representation of patterns of eight types of SYNC codes. In the case of a DVD, one of SYNC code 1 and SYNC code 2 shown in FIG. 15 is selected so as to minimize a DC component of a signal to be recorded.
FIG. 16 shows an example of a structure of a conventional information reproduction apparatus 1600.
The information reproduction apparatus 1600 includes a pickup 1601, a SYNC code detector 1602, a decoder 1603, a memory control circuit 1604, and a memory 1605.
The pickup 1601 reproduces a channel signal recorded on the information recording medium 1201 and thus outputs the reproduced channel signal.
The SYNC code detector 1602 detects a SYNC code included in the reproduced channel signal and thus separates the SYNC code from a modulated code also included in the reproduced channel signal. The modulated code which is correctly synchronized by the SYNC code is output to the decoder 1603.
The decoder 1603 decodes (demodulates) the modulated code and thus generates data for each SYNC frame. The data for each SYNC frame is output to the memory control circuit 1604.
The memory control circuit 1604 generates data based on the data for each SYNC frame, and stores the generated data in the memory 1605.
FIG. 17 shows another example of a structure of a conventional information reproduction apparatus 1700. In FIG. 17, identical elements to those described with reference to FIG. 16 will bear identical reference numerals therewith and description thereof will be omitted.
The information reproduction apparatus 1700 includes a SYNC frame position estimation device 1701 in addition to the elements included in the information reproduction apparatus 1600.
The SYNC frame position estimation device 1701 estimates a correct position of a SYNC frame in accordance with the SYNC code (or variation code) which is output from the SYNC code detector 1602. A signal indicating the position of the SYNC frame is output to the memory control circuit 1604.
The memory control circuit 1604 generates data based on the signal indicating the position of the SYNC frame output from the SYNC frame position estimation device 1701. In this way, data can be stored at a more correct SYNC frame position.
FIG. 18 shows an example of a structure of a conventional information recording apparatus 1800.
The information recording apparatus 1800 includes a pickup 1801, a SYNC code insertion device 1802, an encoder 1803, a memory control circuit 1804, and a memory 1805.
The memory control circuit 1804 reads data stored in the memory 1805 and generates data for each SYNC frame based on the read data. The data for each SYNC frame is output to the encoder 1803.
The encoder 1803 encodes the data for each SYNC frame and thus generates a modulated code. The modulated code is output to the SYNC code insertion device 1802.
The SYNC code insertion device 1802 inserts a SYNC code between the modulated codes and thus generates a channel signal. The channel signal is output to the pickup 1801.
The above-described conventional structures have the following problem. When data other than modulated code (for example, attribute information for protecting copyright, such as an encryption key) is to be recorded on an information recording medium in the state of being embedded in sector data or data in an ECC block, the data structure of the modulated code in the sector data or the data structure of the ECC block needs to be changed. This requires an extensive change of the design of the information reproduction apparatus or the information recording apparatus.
The present invention has an objective of providing an information recording medium for allowing data other than modulated code to be embedded in sector data without changing a data structure of the modulated code in the sector data.
The present invention has another objective of providing an information recording medium for allowing data other than modulated code to be embedded in data in an ECC block without changing a data structure of the ECC block.
The present invention has still another objective of providing an information recording apparatus, an information recording method, an information reproduction apparatus and an information reproduction method for such an information recording medium.